An example of a known fuel pump will be described with reference to FIGS. 24 to 29. As viewed in FIG. 24 in vertical-section, a fuel pump is disposed within a fuel tank (not shown) of a vehicle and comprises a motor section 1 and a pump section 2 assembled at an upper part and at a lower part, respectively, within a cylindrical motor housing 3.
In the motor section 1, a motor cover 4 is mounted at an upper end of the motor housing 3, and a pump cover 5 is mounted at a lower end of the motor housing 3. A motor chamber 6 is formed between the motor cover 4 and the pump cover 5 within the motor housing 3. In the motor chamber 6, an armature 7 is disposed having a commutator 12 on its top end. Upper and lower ends of a shaft 8 of the armature 7 are rotatably supported by the motor cover 4 and the pump cover 5 via bearings 9 and 10, respectively. A pair of magnets 11 is fixed on an inside surface of the motor housing 3. A brush 13 is disposed within the motor cover 4 via a spring 14 so as to slidably contact the commutator 12 of the armature 7. The spring 14 biases the brush 13 to press the commutator 12. The brush 13 is connected via a chalk coil 15 to an outside connecting terminal (not shown).
The motor cover 4 has a discharge port 16 with a check valve 17 incorporated therein. The discharge port 16 is connected to a fuel supply line FL that leads to a fuel injector (not shown) of a vehicle engine.
In the pump section 2, a pump body 18 is assembled with the pump cover 5. The pump body 18 is secured by caulking the lower end of the motor housing 3. A pump housing PH is constructed from the pump body 18 and the pump cover 5 so as to surround an impeller 21 as will be described later. The pump body 18 has a hollow cylindrical axial inlet port 19 therethrough. The pump cover 5 has a hollow cylindrical axial outlet port 20 therethrough. The inlet port 19 and the outlet port 20 in FIG. 24 are viewed as they are substantially coaxial with each other, but are in fact disposed in a spaced-apart relationship from each other in a direction of rotation of the impeller 21. This construction is best shown in FIGS. 25 and 26, which are a cross-sectional view taken along line C--C of FIG. 24 and an exploded sectional view taken along line D--D of FIG. 25, respectively.
The impeller 21 with a disc-like shape has a plurality of vane grooves 22 on opposite axial ends of the impeller 21 along an outer circumference thereof and is rotatably disposed between the pump cover 5 and the pump body 18. The impeller 21 is fitted onto the shaft 8 of the armature 7 as shown in FIGS. 24 and 25. As shown in FIGS. 25 and 26, the pump cover 5 and the pump body 18 are provided with respective flow channels 24 corresponding to the vane grooves 22 of the impeller 21. Both of the flow channels 24 are symmetrically placed in a vertical manner and together form a pump passage 23 extending from the inlet port 19 to the outlet port 20 along the direction of the impeller rotation. The pump cover 5 and the pump body 18 have respective partitions 25 extending from the outlet port 20 to the inlet port 19 in the direction of the impeller rotation for partitioning these two ports. The pump body 18 is shown in FIG. 27 in plan view and in FIG. 28 in a perspective partial cutaway view.
In this fuel pump, the shaft 8 of the armature 7 rotates by supplying electric current to the motor section 1 and rotates the impeller 21 in a counterclockwise direction as shown by a curved arrow in FIG. 25. As a result of this rotation, fuel stored in the fuel tank (not shown) is drawn through the inlet port 19. The drawn fuel is pressurized when passing through the pump passage 23, enters the motor chamber 6 through the outlet port 20, and is discharged through the discharge port 16 to the fuel supply line FL.
Another example of a known fuel pump is disclosed in Japanese Laid-Open Patent Publication 2-215995.